March 3, 2007

CataractDefinitionA cataract is a painless, cloudy area in the lens of the eye that blocks the passage of light to the retina. The retina is the nerve layer at the back of the eye. Cataracts usually cause vision problems.

Alternative NamesLens opacity

Causes, incidence, and risk factorsThe lens of an eye is normally clear. If the lens becomes cloudy, the condition is known as a cataract. Rarely, cataracts may be present at or shortly after birth. These are called congenital cataracts.Adult cataracts usually develop with advancing age and may run in families. Cataracts are accelerated by environmental factors, such as smoking or exposure to other toxic substances, or they may develop at any time after an eye injury. Metabolic diseases such as diabetes also greatly increase the risk for cataracts. Certain medications, such as cortisone, can also accelerate cataract formation.Congenital cataracts may be inherited. The gene for such cataracts is dominant (autosomal dominant inheritance), which means that the defective gene will cause the condition even if only one parent passes it along. Approximately 50% of children in such families will be affected.Congenital cataracts can also be caused by infections of the mother during pregnancy such as rubella, or associated with metabolic disorders such as galactosemia. Risk factors include inherited metabolic diseases, a family history of cataracts, and maternal viral infection.Adult cataracts are generally associated with aging. They develop slowly and painlessly with a gradual onset of difficulty with vision.Visual problems may include the following changes:Difficulty seeing at nightSeeing halos around lightsBeing sensitive to glareVision problems associated with cataracts generally progress to decreased visual acuity, even in daylight.Adult cataracts are classified as immature, mature, and hypermature. A lens that has some remaining clear areas is referred to as an immature cataract. A mature cataract is completely opaque. A hypermature cataract has a liquefied surface that leaks through the capsule and may cause inflammation of other structures in the eye.Most people develop some clouding of the lens after the age of 60. About 50% of people aged 65-74 and about 70% of those 75 and older have visually significant cataracts.Most people with cataracts have similar changes in both eyes, although one eye may be worse than the other. Many people with this condition have only minimal visual changes and are not aware of their cataracts.Factors that may contribute to cataract development are low serum calcium levels, diabetes, long-term use of corticosteroids, and various inflammatory and metabolic disorders. Environmental causes include trauma, radiation exposure, and excessive exposure to ultraviolet light (sunlight).In many cases, the cause of cataract is unknown.

SymptomsCloudy, fuzzy, foggy, or filmy visionLoss of color intensityFrequent changes in eyeglass prescriptionImpaired vision at night, especially while driving, caused by glare from bright lightsProblems with glare from lamps or the sunHalos around lightsDouble vision in one eyeDecreased contrast sensitivity

Signs and testsStandard ophthalmic exam, including slit lamp examinationUltrasonography of the eye in preparation for cataract surgeryOther tests that may be done (rarely) include:Glare testContrast sensitivity testPotential vision testSpecular microscopy of the cornea in preparation for cataract surgery

Treatment

The only treatment for cataract is surgical removal. This is done when a person cannot see well enough with glasses to perform normal activities. For some people, changing glasses, getting stronger bifocals, or using a magnifying lens is helpful enough. Others choose to have cataract surgery.If a cataract is not bothersome, then surgery is usually not necessary. Sometimes there is an additional eye problem that cannot be treated without first proceeding with cataract surgery.Cataract surgery consists of removing the lens of the eye and replacing it with an artificial lens. A cataract surgeon will discuss the options with the patient, and together they will decide which type of removal and lens replacement is best.LENS REMOVAL:

There are 2 types of surgery that can be used to remove lenses that have a cataract.Extracapsular surgery consists of surgically removing the lens, but leaving the back half of the capsule (the outer covering of the lens) intact. High-frequency sound waves (phacoemulsification) may be used to soften the lens to facilitate removal through a smaller incision.Intracapsular surgery involves surgically removing the entire lens, including the capsule. Today this procedure is done very rarely.LENS REPLACEMENT:

People who have cataract surgery are usually fitted with an artificial lens at the same time. The artificial lens is a synthetic disc called an intraocular lens. It is usually placed in the lens capsule inside the eye.Other options include contact lenses and cataract glasses.Surgery can be done in an outpatient center or hospital. Most people do not need to stay overnight in a hospital. The patient will need a friend or family member to assist with travel and home care after outpatient surgery. Follow-up care by the surgeon is important.